1. Field of the Invention
This invention relates in general to a novel P-I-N diode switch for use in secondary radar interrogation devices which are equipped with means for side lobe suppression in the interrogation and reply path (ISLS and RSLS). The P-I-N diode high frequency switch provides for the distribution of interrogation pulses arriving from a transmitter to a first antenna and the reference level pulses passing from the same transmitter to a second antenna by means of two P-I-N type diodes controlled by a driver circuit to render them either blocking or short circuited. One terminal of the P-I-N type diode is respectively connected by way of a T element consisting of three quarter-wave length line pieces on the one hand to the transmitter terminal and on the other hand to the terminal for one of the antennas. The other diode is similarly connected to the terminal of the other antenna, for relaying reception signals from the two antennas to two receivers with each receiver having a corresponding antenna and each receiver having a band pass filter at its input which blocks the transmission signals but allows the reception signals to pass through.
2. Description of the Prior Art
It is known in the primary radar technology to employ an antenna change-over switch for de-coupling transmitter and receiver when one employs a common antenna for transmitting the transmission pulses and for the reception of an echo signal. However, the transmission and reception frequencies are essentially identical so that they can be separated only by means of a switch. Therefore, the fact that the transmission pulse and the reception period are in time succession is utilized. Such an antenna change-over switch can be employed in a secondary radar interrogation device with ISLS and RSLS instead of an antenna switching unit. One can then connect this antenna change-over switch or TR switch to the P-I-N type diode switch for connecting one of the two antennas to the transmitter.